FORMATION OF NICKEL HYDRIDES BY HYDROGEN EVOLUTION IN ALKALINE MEDIA - EFFECT OF TEMPERATURE

The effect of temperature on the hydrogenation of sintered Ni by the h ydrogen evolution reaction (her) in 0.6 M K2CO3 + H2O electrolyte was investigated in the range 25-95 degrees C. At 25 degrees C, hydrogenat ion leads to the formation of three different species, provisionally i dentified as beta-NI-, hexagonal-Ni- and alpha-Ni-hydride phases, base d on their respective redox potentials and thermostability. Their pene tration into the metal ranged from a few tens to a few hundred monolay ers. Above room temperature, the overall efficiency and penetration of Ni hydrogenation increased significantly. Furthermore, there is defin ite evidence that, at T greater than or equal to 65 degrees C, the bet a-Ni-hydride phase evolves into new Ni-hydrogen species of higher ther mal stability, regarding which there is no previous knowledge. The res ults of electrolytic Ni deuteration by electrolysis of K2CO3 + D2O con formed to those obtained in light water. (C) 1998 Elsevier Science S.A . All rights reserved.